求字符串的最长重复子串（java）

  -暴力法

   两个指针实现，复杂度O(n^2)

 

package test;

import java.util.Scanner;

public class Main2 {

	public static String maxRepat(String str) {

		int len = str.length();

		int tmp = 0;

		int startp = 0;

		int max = 0;

		if (str == null || str.length() == 0) {
			return "";
		}

		for (int i = 0; i < len; i++) {
			for (int j = i + 1; j < len; j++) {

				int p1 = i;
				int p2 = j;//兩個指針，向後遍歷

				while (p2 < len) {
					if (str.charAt(p1) == str.charAt(p2)) {
						tmp++;
						p1++;
						p2++;

					} else {
						break;
					}

					if (p1 >= j) {
						break;
					}

				}

				if (tmp > max) {
					max = tmp;
					startp = i;
				}
				tmp = 0;

			}
		}

		//System.out.println(max);
		return str.substring(startp, startp + max);
	}

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		String str = sc.next();

		System.out.println(maxRepat(str));

	}
}

输入 "abcaabc"

输出 "abc"